present invention relates generally to computed tomography imaging and, more particularly, to an apparatus and method of converging light energy for use with computed tomography systems.
Typically in computed tomography (CT) imaging systems, an x-ray source emits a fan-shaped beam toward an object, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is typically dependent upon the attenuation of the x-ray beam by the object. Each detector element of the detector array produces a separate electrical signal indicative of the attenuated beam received by each detector element. The-electrical signals are transmitted to a data processing unit for analysis which ultimately results in the formation of an image.
Generally, the x-ray source and the detector array are rotated with a gantry within an imaging plane and around the object. X-ray sources typically include x-ray tubes, which emit the x-ray beam at a focal point. X-ray detectors typically include a collimator for collimating x-ray beams received at the detector, a scintillator for converting x-rays to light energy adjacent the collimator, and photodiodes for receiving the light energy from the adjacent scintillator.
Typically, each scintillator of a scintillator array has an x-ray entrance area dimensionally equivalent to a light exiting area. As a result, to effectively receive the light energy exiting the scintillator, it is necessary for each photodiode adjacent thereto to have a light receiving area dimensionally similar to the light exiting area of the scintillator. While it is possible to implement a photodiode having a light receiving area smaller than the light existing area of the scintillator, it is certainly not desirable as significant portions of the light energy exiting the scintillator would not be detected by the photodiode. Because a photodiode array having therein a plurality of photodiodes is typically formed on a silicon chip, significant surface area to accommodate the photodiodes is necessary. Reducing the size of the light exiting surface of each scintillator would therefore result in a smaller total active area for each of the photodiodes. Hence, more open or unused portions between active areas of the chip could be available for other purposes.
It would therefore be desirable to have a focused scintillator capable of receiving high frequency electromagnetic energy and converging light energy to a light exiting surface.
The present invention provides a detector for a CT imaging system. The detector includes a focused scintillator for receiving and converting high frequency electromagnetic energy to light energy. The detector further includes a photodiode positioned adjacent to the scintillator and is configured to receive light energy discharged through a light exiting surface of the scintillator. The detector also includes electrical leads connected from the photodiode to a data processing unit. Signal outputs of the photodiodes are transmitted to the data processing unit to facilitate image reconstruction. The CT system provides for a gantry having an output for projecting high frequency electromagnetic energy toward the tapered scintillator. All of which overcome the aforementioned drawbacks.
In accordance with one aspect of the invention, a computed tomography system is provided. The system includes a tapered scintillator array having at least one tapered scintillator therein capable of receiving high frequency electromagnetic energy. The system also includes an output positioned in a gantry for projecting the high frequency electromagnetic energy toward the tapered scintillator array. At least one photodiode forming a photodiode array is optically coupled to the tapered scintillator array for receiving light energy therefrom.
In accordance with another aspect of the invention, a scintillator for a CT system is provided. The scintillator includes an entrance surface defined by a plurality of entrance edges configured to receive high frequency energy. A plurality of walls extend directionally to a plurality of exiting edges configured concentric to the plurality of entrance edges and are configured to converge light energy. The scintillator also includes an exiting surface defined by the plurality of exiting edges configured to discharge the light energy.
The invention also includes a method-of imaging for a CT system. The method includes projecting high frequency electromagnetic energy to a tapered scintillator array formed by a plurality of tapered scintillators. The method further includes converting high frequency electromagnetic energy to light energy and then converging the light energy to a photodiode array formed by a plurality of photodiodes.
Another aspect of the present invention is to provide a method to produce high density detectors for a CT system. The method includes providing a plurality of tapered scintillators forming a tapered scintillator array configured to receive high frequency electromagnetic energy. The method also includes providing a plurality of photodiodes forming a photodiode array optically connected to the tapered scintillator array and configured to receive light energy discharged from the tapered scintillator array. The method also includes connecting a plurality of leads to the photodiode array capable of transmitting electrical outputs of the photodiode array.
Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings.